Beta-carboline drug products

ABSTRACT

A compound of structural formula (I), and pharmaceutically acceptable salts and solvates thereof, wherein the compound is in free drug particulate form, is disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This is the U.S. national phase application of International ApplicationNo. PCT/US00/20981, filed on Aug. 1, 2000, which claims the benefit ofprovisional patent application Ser. No. 60/147,048, filed Aug. 3, 1999.

FIELD OF THE INVENTION

The present invention relates to the fields of pharmaceutical andorganic chemistry, and to a β-carboline compound which is useful for thetreatment of various medical indications where inhibition of type 5cGMP-specific phosphodiesterase (PDE5) is desired. More particularly thepresent invention provides a free drug form of β-carboline particles ina size range allowing for uniform formulation of stable pharmaceuticalcompositions, especially compositions providing desired bioavailabilityproperties heretofore not provided in the art.

BACKGROUND OF THE INVENTION

The biochemical, physiological, and clinical effects of cyclic guanosine3′,5′-monophosphate specific phosphodiesterase (cGMP-specific PDE)inhibitors suggest their utility in a variety of disease states in whichmodulation of smooth muscle, renal, hemostatic, inflammatory, and/orendocrine function is desired. Type 5 cGMP-specific phosphodiesterase(PDE5) is the major cGMP hydrolyzing enzyme in vascular smooth muscle,and its expression in penile corpus cavernosum has been reported (Taheret al., J. Urol., 149:285A (1993) ). Thus, PDE5 is an attractive targetin the treatment of sexual dysfunction (Murray, DN&P 6(3):150-156(1993)).

Daugan U.S. Pat. No. 5,859,006 discloses a class of β-carbolinecompounds, and pharmaceutical compositions containing the β-carbolines,which are useful in the treatment of conditions wherein inhibition ofPDE5 is desired. PCT publication WO 97/03675 discloses use of this classof β-carboline compounds in the treatment of sexual dysfunction.

The poor solubility of many β-carboline compounds useful as PDE5inhibitors prompted the development of coprecipitate preparations, asdisclosed in PCT publication WO 96/38131 and Butler U.S. Pat. No.5,985,326. Briefly, coprecipitates of a β-carboline with polymerichydroxypropylmethylcellulose phthalate, for example, were prepared,milled, mixed with excipients, and compressed into tablets for oraladministration. Studies revealed, however, that difficulties arose ingenerating precisely reproducible lots of coprecipitate product, whichmakes use of coprecipitates less than ideal in pharmaceuticalformulations.

Additionally, clinical studies involving administration of coprecipitatetablets preliminarily revealed that maximum blood concentration of theβ-carboline compound is achieved in 3 to 4 hours, with the average timefor onset of therapeutic effect not yet precisely determined. In thetreatment of sexual dysfunction, such as male erectile dysfunction orfemale sexual arousal disorder, however, a more rapid achievement ofmaximum blood concentration, along with a greater prospect for rapidonset of therapeutic effect, frequently is sought by individualsdesiring more immediate and/or less prolonged effects. Accordingly, aneed in the art continues to exist for orally administrable β-carbolinecompounds and 5-carboline-containing pharmaceutical compositions havingan ability to provide a therapeutic effect within a desirable, or atleast acceptable, time frame.

SUMMARY OF THE INVENTION

The present invention provides particulate preparations of a free drugform of a β-carboline compound having specific and defined particle sizecharacteristics. The defined particle size permits a uniform formulationof stable pharmaceutical compositions. In particular, the presentinvention provides compositions that exhibit a rapid achievement ofmaximum blood concentration of PDE5 inhibitor and/or a rapid onset of atherapeutic PDE5 inhibitory effect.

The present invention provides a compound having the formula (I)

and pharmaceutically acceptable salts and solvates thereof, wherein thecompound is a free drug in particulate form, and wherein at least 90% ofthe particles have a particle size of less than about 40 microns, andpreferably less than 30 microns. Highly preferred particulate forms ofthe β-carboline compound (I) have at least 90% of the particles lessthan 25 microns in size. Most preferred forms of the free compound (I)are those wherein 90% of the particles are less than 10 microns in size.

The present invention provides, therefore, a free form of a β-carbolinecompound, and compositions containing the β-carboline compound, whichcan be used in an effective therapy for conditions wherein inhibition ofPDE5 provides a benefit. The free form of β-carboline compound (I) has aparticle size such that the onset of beneficial effects of PDE5inhibition are exhibited in a relatively short time after oraladministration.

The present invention further relates to pharmaceutical compositionscomprising the particulate compound (I) and one or more pharmaceuticallyacceptable carriers, diluents, or excipients. The invention furtherprovides the use of compound (I) and pharmaceutical compositions fortreatment of sexual dysfunction, e.g., male erectile dysfunction andfemale sexual arousal disorder.

Alternatively stated, the present invention provides for the use of theabove-described particulate forms of compound (I) for the manufacture ofmedicaments for the treatment of sexual dysfunction Specific conditionsthat can be treated by the compound and compositions of the presentinvention include, but are not limited to, male erectile dysfunction andfemale sexual dysfunction, for example, female arousal disorder, alsoknown as female sexual arousal disorder.

Accordingly, one aspect of the present invention is to provide a freedrug particulate form of a compound (I), and pharmaceutically acceptablesalts and solvates thereof, comprising particles of the compound whereinat least 90% of the particles have a particle size of less than about 40microns.

Another aspect of the present invention is to provide a pharmaceuticalcomposition comprising particles of the free drug particulate form ofcompound (I) having a d90 less than 40, and one or morepharmaceutically-acceptable carriers, diluents, or excipients, and amethod of manufacturing the composition.

Yet another aspect of the present invention is to provide a method oftreating sexual dysfunction in patients in need thereof comprisingadministering to a patient in need thereof a therapeutically effectiveamount of a composition comprising particles of the free drugparticulate form of compound (I) having a d90 less than 40 and one ormore pharmaceutically-acceptable carriers, diluents, or excipients. Thesexual dysfunction can be male erectile dysfunction or female arousaldisorder, for example.

Still another aspect of the present invention is to provide apharmaceutical composition comprising: (a) a free drug form of compound(I), and pharmaceutically-acceptable salts and solvates thereof, and (b)one or more pharmaceutically-acceptable carriers, diluents, orexcipients, wherein the composition exhibits a C_(max) of about 180 toabout 280 micrograms/liter or an AUC (0-24) of about 2280 to about 3560microgram hour/ liter, measured using a 10 milligram dose of thecompound. The composition can be a solid, a suspension, or a solution.

Another aspect of the present invention is to provide a pharmaceuticalcomposition comprising: (a) compound (I) and pharmaceutically-acceptablesalts and solvates thereof, and (b) one or morepharmaceutically-acceptable carriers, diluents, or excipients, whereinthe composition exhibits a C_(max) of about 180 to about 280micrograms/liter and an AUC (0-24) of about 2280 to about 3560micrograms hour/liter, measured using a 10 milligram dose of thecompound. The composition can be a solid or a suspension.

Another aspect of the present invention is to provide a pharmaceuticalcomposition comprising: (a) a free drug form of compound (I), andpharmaceutically acceptable salts and solvates thereof, wherein at least90% of the particles have a particle size of less than about 10 microns,and (b) one or more pharmaceutically-acceptable carriers, diluents, orexcipients, and bioequivalent compositions thereof. The composition canbe a solid or a suspension.

These and other aspects of the present invention will become apparentform the following detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 contains plots of % of dissolved compound (I) vs. time, andillustrates the in vitro dissolution characteristics of compound (I) ina varying particle size.

DETAILED DESCRIPTION OF INVENTION

For purposes of the claimed invention as disclosed and described herein,the following terms and abbreviations are defined as follows.

The term “treatment” includes preventing, lowering, stopping, orreversing the progression or severity of a condition or symptoms beingtreated. As such, the present invention includes both therapeutic andprophylactic administration, as appropriate.

The term “effective amount” is an amount of compound (I), or acomposition containing compound (I), that is effective in treating thecondition or symptom of interest. An effective amount of a compound (I)to treat sexual dysfunction in a male is an amount sufficient to provideand sustain an erection capable of penetrating the partner. An effectiveamount of a compound (I) to treat female sexual dysfunction,particularly female sexual arousal disorder, is an amount sufficient toenhance the ability of a female to achieve or sustain an aroused state.

The term “free drug” refers to solid particles of compound (I) notintimately embedded in a polymeric coprecipitate.

The term “suspension” refers to a liquid composition containing freedrug particles of compound (I). The term “solution” refers to a liquidcomposition having compound (I) dissolved therein.

The term “solvate” comprises one or more molecules of compound (I)associated one or more molecule of a solvent, e.g., water or aceticacid.

The term “oral dosage form” is used in a general sense to refer topharmaceutical products administered via the mouth. Solid oral dosageforms are recognized by those skilled in the art to include such formsas tablets, capsules, and aerosols.

The term “pharmaceutically acceptable” means carriers, excipients,diluents, salt forms of compound (I), and other formulation ingredientsthat are compatible with all other ingredients of a composition, and arenot deleterious to an individual treated with the composition.

The nomenclature describing the particle size of compound (I) iscommonly referred to, and is herein, as the “d90.” For example, a d90 of40 (or d90=40) means that at least 90% of the particles have a particlesize of less than 40 microns.

As noted, the present invention provides a compound of structuralformula (I), and pharmaceutically acceptable salts and solvates thereof,characterized in that the compound is a free drug in particulate form,wherein at least 90% of the particles have a particle size of less thanabout 40 microns.

It has been found that by processing(6R-trans)-6-(1,3-benzodioxol-5-yl)-2,3,6,7,12,12a-hexahydro-2-methylpyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione,alternatively named (6R,12aR)-2,3,6,7,12,12a-hexahydro-2-methyl-6-(3,4-methylene-dioxyphenyl)pyrazino[2′,1′:6.1]pyrido[3,4-b]indole-1,4-dione,as disclosed in Daugan U.S. Pat. No. 5,859,006, and represented bystructural formula

to bring the particle size within a particular narrow range,manufacturing capability is enhanced, and pharmaceutical compositionscan be prepared that exhibit an improved bioavailability of the activeingredient, i.e., compound (I).

The present invention encompasses particles of free compound (I) whereinat least 90% of the particles of free drug have a particle size of lessthan about 40 microns (i.e., d90=40), and preferably less than 30microns. More preferably, at least 90% of the particles have a particlesize of less than 25 microns, still more preferably less than 15microns, and to achieve the full advantage of the present invention, d90is less than 10 microns. Particles having a d90 in the nanometer range(e.g., about 200 nm or less, or about 50 nm or less) also arecontemplated. However, nanometer sized particles of compound (I) aredifficult to handle and to formulate, and tend to aggregate. Therefore,a preferred d90 range for the particles of free compound (I) is about 1to about 40 microns.

Preferably, the free drug is crystalline. However, amorphous andpartially amorphous forms of compound (I) also are contemplated, and areincluded within the present invention.

It is understood by those familiar with comminution process techniquesthat the limit set on the size of 90% or more of the particles, usingnormal milling techniques, is a feature to further distinguish theparticulate compounds of the invention from particles exhibiting abroader size distribution. Because of the variation in size encounteredin all matter reduced in size by a comminution process, expressingdifferences in particle size in the manner described herein is readilyaccepted by those skilled in the art.

The present invention also provides pharmaceutical compositionscomprising said particulate compound (I) and one or morepharmaceutically acceptable excipients, diluents, or carriers. Theexcipient, diluent, or carrier can be a solid component of thecomposition or a liquid component. Accordingly, pharmaceuticalcompositions containing particles of free compound (I) can be a solidcomposition, or can be a suspension of free compound (I) particles in aliquid excipient, diluent, or carrier.

The compound of the structural formula (I) can be made according toestablished procedures, such as those detailed in U.S. Pat. No.5,859,006, incorporated herein by reference. The preparation of thecompound of structural formula (I) is specifically provided in U.S. Pat.No. 5,859,006.

Methods of determining the size of particles are well known in the art.For example, the general method of U.S. Patent No. 4,605,517,incorporated herein by reference, could be employed. The following is adescription of one nonlimiting method.

In preparing the particulate compound of the present invention, acompound of structural formula (I), in its raw state, first ischaracterized for size using an instrument adapted to measure equivalentspherical volume diameter, e.g., a Horiba LA910 Laser ScatteringParticle Size Distribution Analyzer or equivalent instrument. Typically,a representative sample of a compound of structural formula (I) isexpected to comprise, in its raw 5 state, particles having a d90equivalent spherical volume diameter of about 75 to about 200 microns,and with a broad size distribution.

After being characterized for size in its raw state, the free drugcompound then is milled, for example using a pin mill under suitableconditions of mill rotation rate and feed rate, to bring the particlesize value within the above mentioned limits of the present invention.The efficiency of the milling is monitored by sampling, using a HoribaLA910 Laser Scattering Particle Size Distribution Analyzer, and thefinal particle size is confirmed in a similar manner. If a first passthrough the mill fails to produce the required size distribution, thenone or more further passes are effected. Other methodologies to prepareparticles as described herein are readily available, including a varietyof milling techniques, such as hammer or fluid energy mills.

The particles of compound (I) in the raw state, as well as after millingor other particle size reduction techniques, are irregular in shape.Therefore, it is necessary to characterize the particles by ameasurement different from actual size, like thickness or length, forexample, by measurement of a property, like intensity and angle ofdiffracted light, and equate that measurement to the diameter of knownspherical particles having the measured same property. The particles arethus allocated an “equivalent spherical diameter.” The values found fromcharacterizing a large number of “unknown” particles can be plotted ascumulative frequency vs. diameter, or in other methods weight vs.diameter, usually adopting percentage undersize values for cumulativefrequency or weight. This provides a characteristic curve representingsize distribution of the sample, i.e., cumulative percentage undersizedistribution curve. Values can be read directly from the curve, or,alternatively, the measurements are plotted on log-probability paper togive a straight line, and the values can be read therefrom.

The d90 equivalent spherical volume diameter thus found is a statisticalrepresentation of the 90% point on a cumulative frequency plot. Asindicated, the d90 equivalent sphere volume diameter of the particles ofthe milled compound of formula (I) are evaluated using a Horiba LA910Laser Scattering Particle Size Distribution Analyzer or other suchequipment recognized by those skilled in the art. Using such instrumentvalues for a suspension of the particles of unknown size are obtained,and the instrument is monitored using a contro sample having particleswithin the size range expected based on statistical analysis of thecontrol sample.

The particle size of compound (I) prior to formulation into apharmaceutical composition can be measured, for example, as follows. Thelaser scattering particle size distribution analysis is effected on asmall sample of the reduced material, which is suspended inapproximately 180 ml of dispersant solution. Prior to sample suspension,a dispersant solution containing 0.1% SPAN 80 in cyclohexane, andpresaturated with compound (I), is prepared. The dispersant solution isfiltered through a 0.2 micron microporous membrane filter to provide aparticle-free dispersant solution. The sample then is added to thedispersant solution until an acceptable level of laser light obscurationis achieved, at which point the particle size distribution is measured.

Triplicate measurements are effected as a minimum a) to provide morereliable measurements and b) to check the equivalent sampling of thesuspended material. The results are automatically recorded and displayedgraphically to give a cumulative % undersize vs. diameter and afrequency percentage vs. diameter for the sample. From this, the d90equivalent spherical volume diameter value is derived (90% cumulativeundersize value).

The compound of structural formula (I) in a free particulate form withinthe above-mentioned limits, then can be mixed with excipients, diluents,or carriers as necessary to provide, for example, dry powders, aerosols,suspensions, suspension or solid filled capsules, and compressed tabletsas oral dosage forms of compound (I).

The particle size of free compound (I) in a pharmaceutical compositionalso can be determined. For example, it is envisioned that the d90particle size of compound (I) can be determined either in a formulateddosage form or as particles of the free drug, by a microscopic method.First, the composition is separated into its individual components, orat least compound (I) is separated from the composition. Persons skilledin the art are aware of separation techniques that maintain the particlesize of compound (I) during separation of compound (I) from thecomposition. For example, water-soluble constituents of the compositioncan be dissolved in water, leaving the highly water insoluble particlesof compound (I) without altering the particle size of compound (I)particles.

The undissolved particles then can be examined under a microscope. Thecrystalline compound (I) can be visually differentiated from amorphouscomposition ingredients. The particle size of compound (I) is determinedby visual inspection and by comparison to standardized particles of aknown size. To ensure that the particle size of compound (I) particlesis being determined, an infrared microprobe can be used to assay theparticles and confirm their identity as compound (I).

Any pharmaceutically acceptable excipients can be used to formulatetablets. The tablets typically contain about 1 to about 20 mg ofcompound (I). Thus, for example, the particulate compound (I) can bemixed with generally recognized as safe pharmaceutical excipients,including liquid diluents, solid diluents (preferably water-solublediluents), wetting agents, binders, disintegrants, and lubricants. See,e.g., Handbook of Pharmaceutical Excipients 2nd Edition, Amer. Pharm.Assoc. (1994). Preferred solid excipients include lactose,hydroxypropylcellulose, sodium lauryl sulfate, microcrystallinecellulose, talc, colloidal silicon dioxide, starch, magnesium stearate,stearic acid, and croscarmellose sodium. Liquid excipients include, forexample, propylene glycol, glycerin, and ethanol. The pharmaceuticalcompositions are prepared by standard pharmaceutical manufacturingtechniques, as described in Remington's Pharmaceutical Sciences, 18thEd. (1990), Mack Publishing Co., Easton, Pa. Such techniques include,for example, wet granulation followed by drying, milling and compressioninto tablets with or without film coating; dry granulation followed bymilling, compression into tablets with or without film coating; dryblending followed by compression into tablets, with or with filmcoating; molded tablets; sachets; suspensions; wet granulation, driedand filled into gelatin capsules; dry blend filled into gelatincapsules; or suspension filled into gelatin capsules. Generally, solidcompositions have identifying marks that are debossed or imprinted onthe surface. The total active ingredients in such pharmaceuticalcompositions comprises from 0.1% to 99.9%, preferably about 1 to 10% byweight of the composition. Preferably, the relative weight percent ofexcipients is as follows:

Quantity (% by weight) Compound (I) 1 to 6 Lactose (diluent) 50 to 75Hydroxypropylcellulose 1 to 5 (binder/diluent) Croscarmellose Sodium  3to 10 (disintegrant) Sodium Lauryl Sulfate 0 to 5 (wetting agent)Microcrystalline Cellulose  5 to 50 (diluent/disintegrant) MagnesiumStearate 0.25 to 2.0  (lubricant)

The specific dose of compound (I) administered according to thisinvention is, of course, determined by the particular circumstancessurrounding the case including, for example, the route ofadministration, the state of being of the patient, and the pathologicalcondition being treated. A typical daily dose contains a nontoxic dosagelevel from about 1 to about 20 mg/day of compound (I). Preferred dailydoses generally are about 1 to about 20 mg/day, particularly 5 mg, 10mg, and 20 mg tablets, administered as needed.

The compositions of this invention can be administered by a variety ofroutes suitable for particulate dosage forms and are preferablyadministered orally. These compounds preferably are formulated aspharmaceutical compositions prior to administration. The selection ofdose is decided by the attending physician.

A compound (I)/hydroxypropylmethylcellulose phthalate coprecipitate wasmanufactured generally by the method set forth in Butler U.S. Pat. No.5,985,326. After preparation of coprecipitate, the coprecipitate wasmilled to provide particles having a relatively large particle size anda relatively wide particle size distribution, i.e., d50=200 microns. Thecoprecipitate there was subjected to a controlled dissolution at a pHthat ordinarily would not release compound (I) from the polymericcoprecipitate component. Applicants found that the coprecipitatecontained a portion of the free drug form of compound (I) not embeddedin the coprecipitate polymer. In clinical studies (see Example 2),applicants further discovered that the blood levels of compound (I)within thirty minutes of administration was attributable to the freedrug present in the coprecipitate compositions.

These results are surprising in view of Butler U.S. Pat. No, 5,985,326which is directed to a method of preparing a solid dispersion ofcompound (I) as coprecipitate. The disclosed process and coprecipitateof Butler U.S. Pat. No. 5,985,326 is directed to providing a soliddispersion of a poorly water-soluble drug, which has an enhancedbioavailability compared to free particles of the poorly water-solubledrug. Butler U.S. Pat. No. 5,985,326 therefore is attempting to avoidthe free form of the drug. Butler U.S. Pat. No. 5,985,326 generallydiscloses milling of the coprecipitate, but fails to disclose the sizeof the coprecipitate particles after milling, and especially fails todisclose either the presence of the free drug form of compound (I) or,if present, a particle size of the free drug form of compound (I).

Based on these observations, it was concluded that a bimodal delivery ofcompound (I) could be achieved with a rapid delivery of the free drugfollowed by a slower delivery of the drug upon the pH sensitive releasefrom the polymeric coprecipitate particles. These observations, in turn,gave rise to the possibility that rapid drug delivery could be effectedby compositions incorporating compound (I) entirely in free drug form,provided that suitable stability could be achieved and that the particlesize of the drug is controlled in a well-defined range for manufactureof the composition. Accordingly, compound (I) in the pharmaceuticalcompositions of the present invention preferably is comprised entirelyof free drug in particulate form, but alternatively the composition cancontain a combination of free drug in particulate form and an embeddeddrug form to provide a bimodal drug delivery. Preferably, the free drugconstitutes greater than 75% free drug (most preferably, greater than90% free drug) of compound (I) in such compositions.

In one embodiment of the present invention, the free drug form ofcompound (I), and pharmaceutically-acceptable excipients, diluents, andcarriers, are present in a pharmaceutical composition that exhibits aC_(max) (i.e., the maximum observed plasma concentration of compound(I)) of about 180 to about 280 μg/L (micrograms/liter), or an AUC (0-24)(i.e., the area under the plasma concentration curve from zero totwenty-four hours) of about 2280 to about 3560 μg·h/L(microgram·hour/liter), measured using a 10 mg dose of the compound. Ina preferred embodiment, the composition exhibits a C_(max) of about 180to about 280 μg/L and an AUC of about 2280 to about 3650 μg·h/L,measured using a 10 mg dose of the compound. In this embodiment, thecomposition can be a solid, e.g., a tablet or powder, by using soliddiluents, carriers, and/or excipients, or a suspension, e.g.,encapsulated in a soft gel, or a solution by using liquid carriers,diluents, and/or carriers.

The C_(max) and AUC (0-24) were determined by analyzing for compound (I)in plasma using a validated LC/MS/MS method, with a lower limit ofquantitation of 0.5 ng/mL. The analytes and an internal standard i.e.,the [¹³C] [²H₃] isotope of compound (I), were extracted from the plasmaby solid phase extraction with 3 mL Empore SD C2 cartridges using 150 μLof 90:10 methanol:water. The analytes were separated using highperformance liquid chromatography with a Penomenex Luna phenylhexyl (4.6mm×100 mm, 5μ) column with a water: acetonitrile (10:90) mobile phase at1.0 mL/minute. Detection was performed using a Perkin Elmer Sciex APIIII Plus tandem mass spectrometer using atmospheric pressure chemicalionization (APCI) in positive ion mode.

It should be understood that C_(max) and AUC (0-24) in plasma is dosedependent. For example, a composition containing a 20 mg dosage ofcompound (I) will exhibit a C_(max) and AUC (0-24) about twice that of acomposition containing a 10 mg dosage. Similarly, a compositioncontaining a 5 mg dosage of compound (I) will exhibit a C_(max) and AUC(0-24) of about one-half that of a composition containing a 10 mgdosage.

Accordingly, the present invention encompasses, for example,compositions containing a 20 mg dosage of compound (I) exhibiting aC_(max) of about 360 to about 560 μg/L and/or an AUC (0-24) of about4560 to about 7120 μg·h/L; and a composition containing a 5 mg dosage ofcompound (I) exhibiting a C_(max) of about 90 to about 140 and/or an AUC(0-24) of about 1140 to about 1780 μg·h/L. Persons skilled in the artare aware of techniques in which the C_(max) and AUC (0-24) ofcompositions containing a dosage of compound (I) different from 10 mgcan be compared or standardized to the C_(max) and AUC (0-24) of acomposition containing a 10 mg dose of compound (I).

In another embodiment, a composition containing compound (I), either asthe free drug alone or as the free drug admixed with a coprecipitate ofcompound (I), and pharmaceutically-acceptable excipients, diluents, andcarriers, exhibits a C_(max) about 180 to about 280 μg/L and an AUC(0-24) of about 2280 to about 3650 μg·h/L. In this embodiment, thecomposition can be a solid or a suspension.

Yet another embodiment of the present invention is a pharmaceuticalcomposition containing a therapeutically-effective amount of particlesof compound (I) and pharmaceutically-acceptable carriers, diluents, andexcipients, wherein at least 90% of the particles of compound (I) have aparticle size of less than about 10 microns, and bioequivalentcompositions thereof. The term “bioequivalent compositions” is definedherein as a composition having a C_(max) of about 180 to about 280 μg/L,and an AUC (0-24) of about 2280 to about 3560 μg·h/L, measured using a10 mg dose of particles of compound (I) having a d90=10 and a human testsubject.

C_(max) and AUC (0-24) be determined by methods well-known to personskilled in the art using humans, primates, dogs, rabbits, or rodents(e.g., rats, mice, guinea pigs, and hamsters), for example, as testsubjects for bioequivalence. Preferred test animals are humans and dogs.

The present invention will be more readily understood upon considerationof the following illustrative examples wherein: Example 1 relates to invitro solubility characteristics of the free drug form of compound (I)of varying particle size; Examples 2 and 3 relate to in vivo tests ofpharmaceutical compositions incorporating a particulate form accordingto the invention in comparison to compositions incorporating acoprecipitate and in comparison to compound (I) of a relatively largeparticle size; and Examples 4 and 5 relate to pharmaceuticalcompositions employing particulate free drug according to the inventionin differing dosage strengths.

EXAMPLE 1

In vitro dissolution tests were performed using compound (I) which hadbeen processed by milling from its raw state particulate form(d90=75-200 microns) into particulate preparations having d90 (microns)values as follows: Lot 1, d90=4; Lot 2, d90=22; Lot 3, d90=55; Lot 4,d90=65; Lot 5, d90=73; and Lot 6, d90=116. Alternative millingtechnologies were employed to develop the various lots. For example, Lot1 was made using a 12 inch pancake style jet mill fed at a rate of 28-30kg/hour with sufficient grind pressure to produce the d90=4 material.Lot 2 was prepared in an Alpine VPZ-160 universal mill equipped with pindiscs (stud plates) and run at approximately 10,000 rpm.

Lots were evaluated in vitro by accurately weighing approximately 10 mgof bulk drug into a test tube, adding 1 mL of purified water, andsonicating for up to 2 minutes to ensure the powder was wetted. The drugslurry was subsequently transferred to a dissolution apparatus vesselcontaining 1000 mL of aqueous 0.5% sodium lauryl sulfate at 37° C. Thetest tube was rinsed with multiple aliquots of warmed dissolution mediumand added back into the dissolution vessel. The paddle speed was 50 rpmand samples were taken at 5, 10, 20, and 30 minutes and subsequentlyanalyzed by HPLC. The results are illustrated in FIG. 1 and demonstrateimproved in vitro dissolution occurs with smaller particle sizes ofcompound (I).

EXAMPLE 2

The improvement in bioavailability and reproducibility of pharmaceuticalcompositions made available by the present invention is demonstrated invivo in humans. The following Table 1 demonstrates the pharmaceuticalcompositions prepared as in Examples 4 and 5 with particulate free drughaving a d90 of 8.4 microns compared to composition incorporating thecoprecipitate of compound (I) with hydroxypropylmethylcellulosephthalate (coprecipitate). In each instance, the tableted compositionwas designed to deliver a 10 mg dose of compound (I).

TABLE 1 In vivo evaluation Pharmaceutical Composition No. of PatientsT_(max) (hrs) Free Drug of Compound (I) 18 2.0 Coprecipitate of Compound(I) 18 3.5

The composition incorporating a particulate free drug form having a d90of 8.4 demonstrated significantly improved T_(max) over a compositioncontaining the coprecipitate (T_(max) is a measure of the time toachieve peak blood levels of a drug, and is indicative of improved onsetof action). The particulate free drug formulation correspondinglyprovided a more rapid rate of absorption of compound (I) into plasma,providing a geometric mean plasma level at 30 minutes of 51 ng/ml(nanograms per milliliter)as compared to 29 ng/ml for the coprecipitateformulation.

EXAMPLE 3

A study was conducted to determine the bioequivalence of tabletscontaining compound (I) in different particle sizes. The tabletscontained compound (I) in a particle size of d90=8.4μ (micron), d90=20μ,or d90=52 μ.

The study was an open-label, randomized, three-period crossover studyconducted on twenty-four (24) healthy male subjects aged 18 to 65 yearsold, divided into two groups of twelve. A single 10 mg oral dose wasadministered with 180 mL of water in each of three treatment periods,and the pharmacokinetics of tablets containing compound (I) in differentparticle sizes were compared.

After dosing, the subjects underwent pharmacokinetic blood sampling.There was an interval of at least 10 days between dosing in eachtreatment period to eliminate any residual compound (I) from theprevious treatment period. The post-study assessment was conductedbetween 7 and 14 days after the final dosing.

Compound (I) was absorbed relatively quickly following oral dosing fromthe d90=52, 30, and 8.4μ particle size formulations. However, the rateand extent of absorption of compound (I) increased with decreasingparticle size. A comparison of C_(max) and AUC (0-24) data showed thatthe difference in absorption between particle size formulations was mostapparent over the first 24 hours after dosing. As used herein, C_(max)is defined as the maximum observed plasma concentration of compound (I),and AUC (0-24) is defined as the area under the plasma concentrationtime curve from zero to twenty-four hours. Both C_(max) and AUC (0-24)are well-known and understood variables to persons skilled in the art.

With respect to C_(max) the d90=52μ and d90=20μ formulations were notbioequivalent to the d90=8.4μ formulation because the 90% confidenceinterval (CI) was outside of the 0.8 to 1.25 equivalence limits. Inparticular, C_(max) was 36% and 23% lower for the 52μ and 20μformulations, respectively, compared to the 8.4μ formulation. The 52μformulation also was not equivalent to the 8.4μ formulation with respectto AUC (0-24), which was 23% lower than the 8.4μ formulation. The 20μand 8.4μ formulations were bioequivalent with respect to AUC (0-24). The8.4μ, 20μ, and 52μ formulations were bioequivalent with respect to AUC,i.e., the area under the plasma concentration time curve from time zeroto infinity.

The study showed that the rate of absorption of compound (I), based onC_(max) and t_(max) (i.e., time to attain maximum observed drug-plasmaconcentration), was slower for the 52μ formulations in relation to the8.4μ formulation. As stated above, C_(max) was not equivalent for the52μ and 20μ formulations compared to the 8.4μ formulation. Mediant_(max) occurred one hour later for the 52μ formulation, but was similarto the 20μ and 8.4μ formulations.

The following table summarizes various pharmacokinetic parameters ofcompound (I) following oral administration of a single 10 mg dose of thed90 52μ, 20μ, and 8.4μ particle size formulations.

d90 = 52μ d90 = 20μ d90 = 8.4μ C_(max) (μg/L) 142 189 224 t_(max) (h)¹⁾3.00 2.00 2.00 AUC (0-24)²⁾ 2201 2667 2849 ¹⁾median data. ²⁾inmicrograms · hour/liter.

This study showed that reducing the particle size of compound (I) inaccordance with the present invention has an impact on the in vivo rateof absorption of compound (I) from a solid dosage form, and, hence, onthe bioavailability of compound (I). For example, from the statisticalanalysis, t_(max) for the 52μ formulation occurred significantly (i.e.,1 hour) later than for the 8.4μ formulation. There was no significantdifference in t_(max) between the 20μ and 8.4μ formulations.Accordingly, onset of a therapeutic benefit attributed to compound (I)after administration is significantly faster for the 8.4μ and 20μformulations compared to the 52μ formulation.

In addition to dissolution and in vivo absorption, another importantaspect of the physical properties of particulate β-carbolinepreparations according to the present invention is the impact on thevarious unit operations of the drug product manufacturing process. Whilethe particle size specification ensures consistent delivery of the drugmolecule to the sites of absorption in the gastrointestinal tract, italso imparts better control during the tablet manufacturing process.

The following formulation examples are illustrative only and are notintended to limit the scope of the present invention.

EXAMPLE 4

The following formula was used to prepare the finished dosage form of atablet providing 10 mg of compound (I).

Ingredient Quantity (mg) Granulation Compound (I) (Lot 1, d90 of 4)10.00 Lactose Monohydrate 153.80  Lactose Monohydrate (Spray Dried)25.00 Hydroxypropylcellulose (EF Extra Fine)  4.00 Croscarmellose Sodium 9.00 Hydroxypropylcellulose (EF)  1.75 Sodium Lauryl Sulfate  0.70Outside Powders Microcrystalline Cellulose (Granular-102) 37.50Croscarmellose Sodium  7.00 Magnesium Stearate (Vegetable)  1.25 Total250 mg

Purified Water, USP was used in the manufacture of the tablets. Thewater was removed during processing and minimal levels remained in thefinished tablets.

Tablets are manufactured using a wet granulation process. A step-by-stepdescription of the process follows. Compound (I) and excipients to begranulated are security sieved. Compound (I) is dry blended with lactosemonohydrate (spray dried), hydroxypropylcellulose, croscarmellulosesodium, and lactose monohydrate. The resulting powder blend wasgranulated with an aqueous solution of hydroxypropylcellulose and sodiumlauryl sulfate using a Powrex or other suitable high shear granulation.Additional water can be added to reach the desired endpoint. A mill canbe used to delump the wet granulation and facilitate drying. The wetgranulation was dried using either a fluid bed dryer or a drying oven.After drying, the material can be sized to eliminate any largeagglomerates. Microcrystalline cellulose, croscarmellose sodium, andmagnesium stearate were security sieved and added to the dry sizedgranules. These excipients and the dry granulation were mixed untiluniform using a tumble bin, ribbon mixer, or other suitable mixingequipment. The mixing process can be separated into two phases. Themicrocrystalline cellulose, croscarmellose sodium, and the driedgranulation were added to the mixer and blended during the first phase,followed by the addition of the magnesium stearate to this granulationand a second mixing phase.

The mixed granulation then was compressed into tablets using a rotarycompression machine. The core tablets were film coated with an aqueoussuspension of the appropriate color mixture in a coating pan (e.g.,Accela Cota). The coated tablets can be lightly dusted with talc toimprove tablet handling characteristics.

The tablets are filled into plastic containers (30 tablets/container)and accompanied by package insert describing the safety and efficacy ofthe formulation.

EXAMPLE 5

By analogous procedures, the following formula was used to prepare thefinished dosage form of a tablet providing 5.0 mg and 20 mg of compound(I).

Quantity Quantity Ingredient (mg) (mg) Granulation Compound (I) (Lot 1,d90 of 4)  5.00 20.00 Lactose Monohydrate 109.66  210.19  LactoseMonohydrate (Spray Dried) 17.50 35.00 Hydroxypropylcellulose  2.80  5.60Croscarmellose Sodium  6.30 12.60 Hydroxypropylcellulose (EF)  1.22 2.45 Sodium Lauryl Sulfate  0.49  0.98 Outside Powders MicrocrystallineCellulose (Granular-102) 26.25 52.50 Croscarmellose Sodium  4.90  9.80Magnesium Stearate (Vegetable)  0.88  0.88 Total 175 mg 350 mg

The principles, preferred embodiments, and modes of operation of thepresent invention have been described in the foregoing specification.The invention that is intended to be protected herein, however, is notconstrued to be limited to the particular forms disclosed, because theyare to be regarded as illustrative rather than restrictive. Variationsand changes may be made by those skilled in the art without departingfrom the spirit of the invention.

What is claimed is:
 1. A free drug particulate form of a compound havinga formula

or pharmaceutically acceptable salts and solvates thereof, comprisingparticles of the compound wherein at least 90% of the particles have aparticle size of less than about 40 microns.
 2. The free drugparticulate form of claim 1 wherein at least 90% of the particles have aparticle size of less than about 25 microns.
 3. The free drugparticulate form of claim 1 wherein at least 90% of the particles have aparticle size of less than about 15 microns.
 4. The free drugparticulate form of claim 1 wherein at least 90% of the particles have aparticle size of less than about 10 microns.
 5. A pharmaceutical solidcomposition comprising the free drug particulate form as in any one ofclaims 1-4 and one or more pharmaceutically-acceptable carriers,diluents, or excipients.
 6. A method of treating sexual dysfunction in apatient in need thereof, which comprises administering to the patient atherapeutically effective amount of a solid composition comprising thefree drug particulate form as in any one of claims 1-4 and one or morepharmaceutically-acceptable carriers, diluents, or excipients.
 7. Themethod of claim 6 wherein the sexual dysfunction is male erectiledysfunction.
 8. The method of claim 6 wherein the sexual dysfunction isfemale sexual arousal disorder.
 9. A method of manufacturing the freedrug particulate form of claim 1 comprising: (a) providing a solid, freeform of the compound, and (b) comminuting the solid free form of thecompound to provide particles of the compound wherein at least 90% ofthe particles have a particle size of less than about 40 microns. 10.The method of claim 9 further comprising the step of admixing theparticles of step (b) with one or more pharmaceutically-acceptablecarriers, diluents, or excipients.
 11. A pharmaceutical solidcomposition prepared by admixing particles of a compound having aformula

or a pharmaceutically acceptable salt or solvate thereof, with one ormore pharmaceutically acceptable carrier, diluent, or excipient, whereinthe particles of the compound have a d90=40 or less.